| Background:Skeletal muscle cells are capable of expressing immunobiological properties and can be defined as non-professional antigen presenting cells.They are capable of presenting antigens through major histocompatibility complex molecules(MHC),expressing costimulatory molecules and secreting soluble cytokines and chemokines,which actively participate in the pathophysiological processes of inflammatory myopathy in a pro-inflammatory or anti-inflammatory manner.Understanding the exact role of skeletal muscle cells may help to identify new therapeutic targets for these devastating diseases.The unfolded protein response(UPR)is an adaptive response aimed to restore endoplasmic reticulum homeostasis under ER stress conditions.It has shown that the UPR function goes far beyond its traditional identification and intersects with seemingly unrelated functions such as innate immunity and antigen presentation.UPR is also thought to be involved in the repair and regeneration of skeletal muscle and also in the regulation of muscle remodeling.However,involvement of the UPR in regulation of the immunological properties of myofibers is still unknown.Objective:To analyze the effects of inflammatory micro-environment induced by the acute muscle injury and inflammatory stimuli on the UPR signal activation in muscle tissue and muscle fibers;to clarify the effect of the UPR signaling pathway on the immune phenotype of muscle fiber induced by the inflammatory stimuli in vitro;and further analyze the deep mechanism of the UPR signal effect on immunophenotype of myofibers.Methods:IF and qRT-PCR were used to analyze the correlation between activation of UPR-IRE1? signaling pathway and the acute muscle injury(caused by CTX)and in vitro inflammatory stimuli.Small molecule chemical inhibition was used to impair UPR-IRE la signaling pathway activation function whereas Western blot,Luminex were used to study the effect of UPR-IRE1? pathway activation on muscle fiber immunological characteristics in inflammatory environment.The above-mentioned techniques were used to clarify effect of that UPR-IRE1? signaling pathway affects on the expression of myofibrillar molecules through p38 MAPK signaling pathway.The effect of UPR-IRE1? anxis on myofibers immune function was further investigated by flow cytometry.Results:1.CTX intramuscular injection caused acute muscle damage.During the regeneration process,inflammatory exudation increased in muscle tissue,and the markers of UPR signaling pathway in muscle tissue were up-regulated at the gene level and protein level.IRE1? and eIF? pathway were obviously activated.The fluctuation downgraded as muscle tissue regenerated and recoveed.2.In vitro interferon-gamma(IFN-?)mimicked the inflammatory environment and induced primary myotubes to up-regulate the markers of IRE1? and eIF?signaling pathway.3.Inhibition of UPR activity,especially IRE1? a pathway,further up-regulated the inflammation-related molecules induced by IFN-? in the primary myotubes.4.IFN-? can induce the activation of p38 MAPK signaling pathway in myotubes,which can be further the enhanced by the inhibition of UPR activity.At the same time,inhibition of p38 MAPK activity significantly decreased the expression of myotube immune-related molecules in inflammatory environment.Under these conditions,the expression of inflammatory molecules in the myotubes were significantly inhibited,even under the inhibition of UPR activity.5.In an inflammatory environment,inhibition of the IRE1? signaling pathway promoted proliferation of CD8+ T cells co-cultured with primary myotubes and OVA,whereas,inhibition of the p38 MAPK signaling pathway reverses this promoting effect.Conclusion:Activation of the UPR signaling pathway in skeletal muscle is observed in the inflammatory environment.Inhibition of IRE1? pathway activity can promote the expression of muscle fiber immunophenotype,and promote the interaction between myotubes and T cells.The promotion effect may be achieved through the p38 MAPK signaling pathway. |
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